1. Field of the Invention
The present invention relates to an image processing apparatus, method, and program. In particular, the present invention relates to an image processing apparatus, method, and program which is suitably used for frame rate conversion.
2. Description of the Related Art
To date, frame-rate conversion processing, in which an interpolated frame is generated between consecutive frames of an image signal so that a frame rate of the image signal is converted, has been widespread. In the frame-rate conversion processing, a motion vector is detected from two frames having different display time, and an interpolated frame is generated by motion compensation using the motion vector.
Incidentally, in a video signal of a content, etc., there are sometimes an area in which a content itself is displayed and a band of area surrounding that area (in the following, called a still-zone area) on an image. In a band of still-zone area disposed at the edge of such an image, a same image, for example, a black image or an image having a design of a predetermined pattern, is continuously displayed. This still-zone area is generally called a black belt, a side panel, a letterbox, etc.
When frame-rate conversion is performed on a video signal of an image including such a still-zone area, if an interpolated frame is generated without considering the still-zone area, detection of motion vectors and motion compensation are performed using the pixels of the still-zone area, thereby deteriorating the image quality of the interpolated frame image. Accordingly, in the frame-rate conversion processing, it is necessary to reliably detect a still-zone area on an image, and to perform detection of motion vectors and motion compensation on a suitable area on the image, that is to say, on an area excluding the still-zone area.
For example, as a method of detecting a still-zone area, proposals have been made on a method of detecting a low-luminance-value area on an image as a still-zone area (for example, refer to Japanese Unexamined Patent Application Publication Nos. 2005-203933 and 2006-229781) and a method of detecting a still-zone area using a correlation of luminance values and frequencies (for example, refer to Japanese Unexamined Patent Application Publication Nos. 7-29820 and 11-8799).
Also, there is a widespread method of detecting a still-zone area by comparing luminance values of pixels in the vicinity of a center of an image and luminance values of pixels around the edge of the image (for example, refer to Japanese Unexamined Patent Application Publication No. 2007-150379). Also, there is a widespread method of detecting a still-zone area by determining whether there is an additional image at the time of decoding an image signal (for example, refer to Japanese Unexamined Patent Application Publication No. 2006-339737).